Method and apparatus for distillation control



Jan. 20,1931. w. K. LEwls K 1,789,339

METHOD AND APPARATUS FOR DISTILLATION CONTROL Filed March s1, 192e zsneets-sneet 1 Jan. 2 0, 193.1.. w, K, LEWIS 1,789,339

` METHOD AND APPARATUS FOR DISTILLTI-ON CONTROL Filed March 51, 1928 2 Sheets-Shet 2 f4l 14a STEAM Ov7-La7' f/Gf -5 l I vwanboz.'

mmmofmw Patented Jan. `20, 1931 UNITED STATES PATENT OFFICE WARREN X. LEWIS, 0F NEWTON, MASSACHUSETTS, ASSIGNOB'` TO STANDARD OIL DEVELOPMENT COMPANY, A CORPORATION OF DELAWARE l METHOD Nn APPARATUS ron DIsnLLATIoNf CONTROL Application led March 31, 1.928. Serial N').,268,135.y

This invention relates to an apparatus for determining thelowest boiling constituents of a mixture of hydrocarbons and to a method and apparatus for determining and regulating the lowest boiling constituents of the bottoms obtained on fractionating petroleum oils.

Fig. 1 of the drawing is a vertical plan with parts in section showing a .bank of stills for the fractional distillation of petroleum oils combined with a control apparatus pursuant to my invention, and

Fig. 2 is a horizontal plan of part of Fig. 1, and

Fig. 3 is a Vertical cross section through a preferred form of apparatus which I have devised for determining the boiling point of the lowest boilin'g constituents of a mixture of hydrocarbons.

In accordance with my method, I automatically and periodically or continuously divert a minor part of the bottoms, the composition of which is to be controlled, partially distill the part diverted under conditions of substantially constant heat input and measure the temperature of the vapor produced. This vapor is preferably rectified under substantially constant conditions and the temperature measured subsequent to rectification. In either event, the temperature of the vapor furnishes a regular or continuous indication of the lowest boiling constituents present in the bottoms. I may utilize this indication as a basis for the manual control of the major distillation making' such corrections manually as are necessary to hold the said major distillation to a predetermined separation but my preferred method is to make the control of the major distillation entirely automatic by utilizing the temperature of the vapor produced in the said control distillation operating through suitable mechanism, to continuously or periodically modify the factor's affecting the major'distillation in order to check divergences from the predetermined point and restore the system thereto. -De vices to prevent over-correction or hunting/I may be employed.

y invention will be clearly understood from the following exposition of my method under conditions of partial condensation and,

thereafter passes off through the vapor line 1c. The remnant oil flows continuously from 1 through the pipe 7 into the still 2 in Which it is further partially vaporized. The vapor so produced is rectified in the column 2b ,to produce an overhead vapor which is diverted from the system through the vapor line 20. The remnant crude oil passes from still 2 to still 3 through the oil line 8. It is again partially vaporized in still 3 and the vapor produced is rectified in the rectifying column 3b to produce an overhead vapor which is diverted from the system through the vapor line 3c. It will be assumed, by way of practical example, that, the stills 1, 2 and 3 are operating to remove gasoline from a crude oil and that the removal has been nearly completed in the still 3, leaving a bottoms containing only a .small quantity of gasoline which is'conducted away through the pipe 9. It will, of course, be understood that any corresponding system for removing gasoline or a first distillate from a petroleum oil may be similarly employed and that the use of a4 number of stills operating in series or of rectifying columns or other devices to improve the fractional separation is entirely optional. In order to effect the maximum possible recovery of gasoline while accurately controlling the endpoint or final boiling point of the mid-section of the rectifying column 4b which communicates with the cut still. The oil may be elevated into the column 4b by the use of a steam lift consisting of the down flowing and up flowing sections of the pipe 9 and the steam jet 9a. Any equivalent transferring device, such as a pump, may be alternatively employed.

The cut still is usually operated with a higher reflux ratio and a lower out ut overhead than the preceding stills in t e series. Partial condensation for the rectifying tower 4b is provided by flowing a cooling medium through the coil 4d in the upper part of said tower. The final fraction of gasoline vapor after rectification in column 4b passes off through the vapor line 4c. The residue crude oil, substantially free from gasoline; passes off through the pipe 10 to the still 5 for further separation of higher boiling point distillates, such as kerosene.

The rectifying columns, hereinbefore described, are all equipped with transversepartitions, overflow pipes and vapor distributors or corresponding means to promote the countercurrent contact of ascending vapor and descending condensate.

The apparatus 11 which I have devised is attached to and placed in communication with the flow line 10 by coupling it to the flange 12 of the T 13, which is a standard pipe fitting in the said flow line 10. The apparatus 1l serves to constantly measure the boiling point of the lowest boiling constituents of the bottoms flowing through the pipe 10. This temperature may be observed by means of a thermometer or any other equivalent measuring device and may, as previouslyl stated, furnish the basis for the manual control of the still 4 but the temperature is preferably measured by means of a thermocouple 14 in the path of the vapor generated in the control still and the E. M. F. developed by the said'thermocouple is transmitted through the leads 15 and 16 to the instrument box 17. The instrument box 17 receives an unmodified current either alternating or direct and preferably at one of the generally available voltages, through the leads 18 and 19 and delivers a current through the leads 20, 21 and 22.

The temperature of the lowest boiling constituents as shown by the control still, which it is desired to retain in the bottoms, is then determined by experiment or as the result of previous runs in the apparatus 'or in any other suitable manner.

The instrument box 17 is adjusted so that vany variation upwardly from this tempera'-v ture or corresponding increase in the E. generated in the thermocouple 14 operating through the instrument box 17, will set up a modified 4current through the leads 20. 21 and 22 having certain characteristics, while a deviation downwardly from the said predetermined temperature and corresponding decrease in E. M. F. of the thermocouple 14,

lheat supplied tothe still is decreased until the temperature measured by the thermocouple 14 has returned to the desired point.'

This control may be accomplished, Vfor example, by the use of agas burner controlled by motors such that when current is supplied to one of the motors by means of the leads 20 and 21, the motor operates to further open the valve controlling the su ply of gas to the burner and supplies an a ditional amount of heat to the still 4, whereas 'a current flowing through the leads 21 and 22 operates a dif-4 ferent motor which closes or partly closes the valve, controlling the supply of gas to the burner. It will, of course, be understood that any 'other method of regulating the major distillation may, pursuant to my invention, be combined with the apparatus 11 and controlled by it. Amore detailed description of the instrument box 17 and the burner adjusting mechanism 23 is not given for the reason that such equipment may be easily designed or adapted to this purpose and the construction thereof is not a part of my invention.

The general arrangement of control apparatus 11 and still 4 appears in horizontal plan in Fig. 2.

Referring specifically to Fig. 3, the control apparatus comprises the hood 4or casing 24 provided with a top closure 25 preferably threaded thereto. The casing'24 carries a fflange 24a at the lower end adapted to cooperate with the flange 12 of the T 13 to place the said casing in free communication with a flow line 10 which conducts the bottoms lfrom the still 4 to the still 5.

The casing 24 is surrounded by the thermal insulation 246. Within the casing 24 and suspended from the top closure 25is the control still 28 and .ancillary apparatus. The control still 28 receives a substantially continuous supply of oil from the body of still Vbottoms 29, which surrounds it, by means of the sharp-mouthed orifice meter 30. The still bottoms accumulates in the control still 28 up to the level 31, any excess passing ofi continuously vthrough the overflow 32 provided with the trapl 34. The heating element, located in the control still 28, may be of any suitable type but preferably V consists of an electrical resistance 35 in a metal casing 36 supplied with current by means of the leads 37 and 37a. These leads may be carried to the exterior between the flanges 12 and 24a and gasketing means may be employed between the flanges which means is grooved or cut to permit the leads to extend -to the exterior.

While the amount. of heat supplied to the control still may vary over considerable limits, I preferably maintain it substantially constant and this may be effected by supplying suitable electric current to the heating element from any electric circuit of substantially constant voltage. The amount of heat supplied is sufficient to partially vaporize the still bottoms in 28. The vapor ascends the column 27 which is preferably packed with a divided material presenting considerable surface such as short sections of tubing 38 to facilitate rectification. The 'column 27 is preferably surrounded by thermal insulation 29. To further improve the rectification which takes place in the column 27, I preferably partially condense vapor at or near the top of the column 27 and this partial condensation is preferably accomplished under conditions so controlled as to provide a substantially constant reflux. The specific partial condensing apparatus which I prefer for this purpose comprises the receptacle 40 receiving a low boiling point liquid such as water through the inlet 41 and provided with the outlet 42 through which any excess, above that necessary to maintain a definite level, is diverted.

The substantially continuous and controlled supply of the low boiling point liquid is passed by means of t-he sharp-mouthed orifice 43 into the evaporator 44. The low boiling liquid is so chosen that it will be'evaporated in 44 at the temperature of condensation of the hydrocarbon vapor in the column 27 and is supplied in such a quantity that 1t will be completely evaporated. The vapor products of evaporation escape through the outlet 45. I achieve in this manner a reflux in the column which is substantially independent of the temperature of the liquid introduced to the partial condenser 44. The rectified hydrocarbon vapor passes from the control column 27 by means of the vapor outlet 46 communicatin with the vapor duct 47. Outlet 46 is preferably surrounding by thermal insulation 46a. The thermocouple 14 for measuring the temperature of the rectified vapor is preferably placed in the vapor duct 46 so that the junction 14a is directly in the path of the issuing vapor at a point at which the said vapor has had no opportunity to cool. Vhile the va or, after passing the thermocouple 14, may. e vented in any way, I preferably condense it by passing a cooling liquid in indirect heat exchange relationship therewith, using for this purpose the condenser 48 and after condensation combine it with the excess liquid passing from the control still 28 through the overow pipe 34, thereafter diverting the stream of llquid to an accumulator through the pi e 49.

The space between the insu ation 29 surrounding the rectifying column of the control still 27 and the caslng 24is in free communication-with the oil flowin in the pipe 10 and this being at an elevate temperature operates to minimize loss of heat from the column pipe 10.

In my preferred method of operation, I maintain a substantially constant thermal gradient between the finally rectified vapor and a point immediately beneath the partial condenser in the rectifyin column 4b, notwithstanding variations t ing place in the still 4. In order to accomplish this, I measure the temperature of the finished overhead vapor leavin the column 4b shown on Fig. 1, by means o thermocouple 50. I also measure the temperature of the contents of the column at a point beneath the partial condenser 4d by means of thermocouple 51, which may be located at any suitable oint in the column although it is prefera ly placed in or immediately above the liquid on the topmost plate. The E. M. F.s generated in thermol teristics and any decrease in the difference.

between the E. M. F.s of the respective thermocouples will set up a modified current flowing through the said leads, having the converse characteristics. This modified current operating throu h suitable control mechanism 58 varies 51e amount of cooling fluid passing throughthe partial condenser 4d so as to increase the amount of partial condensation if the temperature differential between the points at which the thermocouples are located is not sufiicently great and to diminish the amount of partial condensation, in case it is too great. In this manner,a substantially constant rectifying effect is obtained in the column notwithstanding variations in the amount of vaporization in the still 4.

The foregoing description is for purposes of illustration. My method may be carried vunder conditions of substantiall out in apparatus other than that specifically described and it is my intention that the invention belimited only bythe appended claims or their equivalents, in which I have endeavored to claim broadly all novelty inand an unvaporized residuum, rectifying the.

vapor produced, measuring the temperature of the rectified vapor, and modfyin the condition of the first mentioned distillation to the extent necessary to hold such temperature near a. predetermined point.

2. The method of controlling the lowest boiling constituents of bottoms produced on the fractional distillation of petroleum oils, which comprises continuously abstracting at a substantially uniform rate a minor part of the bottoms to be controlled, heating same uniform heat input to produce vapor an an unvaduced ing porized residuum, conducting away unvaporized residuum, rectifying the vapor prounder conditions adapted to maintain a substantiallv constant reflux, measuring the temperature of the rectified vapor produced, and modifying th'e condition of the first mentioned distillation to the extent necessary to hold such temperature near a predetermined point.

3. The method of controllin the lowest boilin point constituents of ttoms ob-` taine on the fractional distillation of petroleum oils, which comprises continuously ahstractin a minor part of the bottoms to bc control ed, heating same under conditions of substantially uniform heat input to produce vapor, and an unvaporize residuum, measuring` the temperature of the vapor pro-y duced, causing variations of such temperature to automatically alter the conditions affectthe first-mentioned distillation to the extent necessary to hold'the 'said temperature V near a predetermined point.

4. The method of controllin the lowest bo'ling point constituents of toms obtained on the fractional distillation of petroleum oils, which comprises continuously ahstracting at a substantially uniform rate a minor part of the bottoms to be controlled, heating same under conditions of substantially uniform heat input to produce vapor and an unvaporized residuum, rectifying the vapor produced, measuring the tempera-ture of the rectified vapor and causing variations of such` temperature to automatically alter the conditions affecting the first mentioned distillation to the extent necessary to hold the l said temperature near a predetermined point.

5. The method of controlling the lowest boiling pointconstituents of bottoms produced on the fractional distillation of petroleum oils, which comprises continuously abstracting at a `substantially' uniform rate a minor part of thebottoms to be controlled, heating same under conditions of substantially uniform heat input to produce vapor and an unvaporized residuum,l conductlng away unvaporized residuum, rectifying the vapor produced under conditions adapted to maintain a substantially constant refiux, measuring the temperature of the rectified vapor produced and causing variations of such temperature to automatically alter the conditions affecting the first mentioned distillation to the extent necessary to hold the said temperature near a predetermined point.

6. The method of controlling the lowest boiling point constituents of bottoms obtained on the fractional d'stillation of petroleum oils, which comprises continuously abstracting a minor part of the bottoms to be con trolled, heating same under conditions of substantially uniform heatinput to produce vapor and an unvaporized residuum, interposing a thermocou le in the path of the vapor produced an causing variations in the E. M. F. generated in said thermocouple from a. predetermined ,point to actuate modifications in the condition of the first mentioned distillation necessary to hold such E. M. F. near a redeterxnined point.

'7. The method) of controlling the lowest boiling point constituents of bottoms obtained on the fractional distillation of petroleum oils, which comprisescontinuously abstracting a minor part of the bottoms to be controlled,-heating same under conditions of substantially uniform heat input to produce vapor, and an unvaporized residuum, measuring the temperature of the vapor produced,

rectifying the vapor produced, interposing a thermocouple in the path of the rectified vapor and causin variations in the E. M. F. generated in sai thermocouple from a predetermined point to actuate modifications in the condition of the first mentioned distillation necessary to hold such E. M. F. near a predetermined point.

8. The method of controlling the lowest boiling point .constituents of bottoms' obtained on the fractional distillation of petroleum oils,which comprises continuously abstracting a minor part o f the bottoms to be controlled, heating same'under conditions of substantially uniform heat in ut to produce vapor and an unvaporizedp residuum, rectifyingthe vapor produced under conditions adapted to maintains. substantially constant reflux, interposing a thermocouplev said thermocouple from a predetermined point to actuate modifications in the condition of the first mentioned distillation necessary to hold such E. M. F, near a predetermined point. z

9. The method of controlling the fractional distillation of petroleum oils, which comprises heating petroleum oil to produce vapor and a bottoms, rectifying the vapor produced in a rectifying Zone under conditions of partial condensation, continuously abstracting a minor part of the bottoms, heating the abstracted part under conditions of a substantially uniform heat input to produce vapor and an unvaporized residuum, measuring the temperature of 'the Vapor produced, causingl variations of the measured temperature from apredetermined point to automatically alter the conditions affecting the first mentioned distillation to Athe extent necessary to hold the said temy residuum, means for conducting away unvaporized residuum, means for separately conducting away the vapor produced, means for measuring the temperature of the vapor produced, and means for causing variations of the measured temperature from a. predetermined point to automatically alter the conditions affecting the first mentioned distillation to the extent necessary to hold the said temperature near a predetermined point.

11. An apparatus for controlling the lowest boiling point constituents of bottoms obtained on the fractional distillation of petroleum oils, which comprises means for tent necessary to hold the said temperature f troleumoils, which comprises means for` abstracting a minor lpart of the bottoms to be controlled at a substantially uniform rate, means for heating the abstracted part under conditions of substantiallyv uniform heat input to produce vaporvand an unvaporized residuum, means for conducting away unvaporized residuum, means for rectifying the vapor produced, means for maintaining a substantially constant reflux during the rectification of said vapor produced, means for measuring the temperature of the rectied vapor, and means for causing variations of the measured temperature from a predetermined point to automatically, alter the conditions affecting the first mentioned distillation to the extent necessary to hold the said temperature near a predetermined point.

WARREN K. LEWIS.

abstracting a minor part of the bottoms to bel controlled at a substantially uniform rate,

means for heating the abstracted part under conditions of substantially uniform heat input to produce vapor and an unvaporzed residuum, means for conducting away unvaporized residuum, means for rectifying the vapor produced, means for measuring the temperature of the rectified Vapor, and means for causing variations of the measured temperature from a predetermined point to automatically alter theconditions affecting the first mentioned distillation -to the exl 12oV 'lauf 

